node capture: animating a shaderPaint's opacity makes every position in the invocation render unshaded

[k9p5]

node capture: animating a shaderPaint's opacity makes every position in the invocation render unshaded

Summary

When dapi node capture is given more than one -t position and any one of those
positions falls where a <shaderPaint>'s animated opacity is between 0 and 1, every
frame in that invocation comes back with the shader skipped — including positions that
render correctly when captured on their own.

The frames are silently wrong: they render as if the <shaderPaint> were absent, with no
error on stdout and nothing in dapi logs.

Expected

Each requested position renders the same as an export would, with the shader applied.
shader-paint.md states that exports wait for pipeline compilation; node capture is
documented as the way to check a composition, so it should wait too.

Actual

Measured on a composition where a procedural <shaderPaint> (no media paint below it, in a
<rect>) draws a bright ribbon in the lower half of the frame. The paint's opacity is
driven by an anime.js timeline through a solid-js store, and fades 1 -> 0 starting at 13.57s.
Value quoted is the brightest pixel in the lower half; (22,22,22) is the bare background,
i.e. no shader.

invocation	11.62s	12.90s	13.70s	13.90s
-t 11.62 12.90 (opacity == 1 at both)	(224,233,255)	(163,168,189)	—	—
-t 11.62 13.70	(22,22,22)	—	(22,22,22)	—
-t 13.62 13.90 (both mid-fade)	—	—	(22,22,22)	(22,22,22)
-t 13.70 (alone)	—	—	(155,160,177)	—
-t 13.90 (alone)	—	—	—	(152,157,175)

Bisected on the fade boundary: -t 11.62 13.50 is fine, -t 11.62 13.60 fails. The fade
starts at 13.57.

What is and isn't the trigger

• Not the number of positions — -t 11.7 11.9 12.1 12.3 (four) renders correctly.
• Not the span between positions — -t 11.62 13.40 (1.8s) renders correctly.
• Not animated uniforms — the control row above animates seven f32 uniforms per frame
  and renders correctly.
• Not contact sheet vs --separate — both behave the same.
• Not a cold pipeline alone — repeating the failing invocation keeps failing, and
  repeating the single-position invocation keeps succeeding, indefinitely.

The one variable that flips it is the paint's own animated opacity.

Guess at the mechanism

Reads like the multi-position path patches the paint's opacity between renders, that patch
invalidates or recompiles the shader pipeline, and — pipeline compilation being async — the
capture doesn't wait for it, so the whole batch rasterises unshaded. A single-position
capture never patches, so it never trips.

Why it matters

This is the verification path. An author checking a shader composition sees frames with no
shader in them and reasonably concludes their own shader or paint stack is broken. It cost me
a couple of hours and one wrong diagnosis: I concluded a <shaderPaint> needs an opaque paint
beneath it to render at all, removed and re-added that paint, and reordered the scene's layers
chasing it — all on frames that were lying. The trap is that the failure looks exactly like a
composition bug, and the "fix" (capture one position at a time) looks exactly like a flake.

Secondary, unconfirmed, possibly unrelated

I could not get a standalone minimal repro to render a <shaderPaint> at all. In a fresh
project, this module renders solid black in node capture and in the app canvas
(dapi screenshot), with no WGSL error in dapi logs:

const RED = `
  @fragment
  fn main(@location(0) uv: vec2f) -> @location(0) vec4f {
    return vec4f(1.0, 0.0, 0.0, 1.0);
  }
`;

export default function Repro() {
  return (
    <rect scene="repro" name="Repro" width={1920} height={1080} fill="#161616">
      <rect name="Shaded" x={0} y={540} width={1920} height={540} fill="#000000" start={0} end={3}>
        <shaderPaint wgsl={RED} />
      </rect>
    </rect>
  );
}

The same construction (procedural <shaderPaint> on a non-root <rect>, no media below)
renders fine in my real composition, which differs mainly in driving a useTicker() clock and
a solid-js store. If a procedural shader paint needs a running ticker to draw, that is worth
documenting; if it doesn't, this is a second bug.

Repro

dapi mount main.jsx
dapi node capture <scene> -t 11.62 12.90 -S -o ok    # both shaded
dapi node capture <scene> -t 11.62 13.70 -S -o bad   # both unshaded; 13.70 is mid opacity-fade
dapi node capture <scene> -t 13.70 -S -o single      # same position alone: shaded

Environment

dapi	0.129.0
platform	darwin 25.5.0 (arm64)
node	v20.19.0
app	running

App logs

13:31:59.130 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:31:59.130 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:32:28.954 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:32:28.954 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:33:51.672 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:33:51.672 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:34:34.819 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
13:34:34.819 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:07:08.524 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:07:08.524 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:08:24.495 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:08:24.495 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:09:38.567 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:09:38.567 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:10:15.172 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:10:15.172 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:11:03.604 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:11:03.604 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:12:02.211 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:12:02.211 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:26:47.088 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:26:47.088 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:32:45.192 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:32:45.192 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:34:45.349 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:34:45.349 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:43:13.345 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:43:13.345 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:44:08.070 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:44:08.070 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:51:06.863 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:51:06.864 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:54:40.699 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
16:54:40.699 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:00:04.370 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:00:04.370 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:02:15.685 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:02:15.685 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:03:43.441 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:03:43.441 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:06:11.692 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:06:11.692 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:06:43.398 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:06:43.398 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:07:30.377 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:07:30.377 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:08:44.148 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:08:44.148 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:15:51.870 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)
17:15:51.871 [error] Error drawing <HtmlPaint> content: InvalidStateError: Failed to execute 'drawElementImage' on 'CanvasRenderingContext2D': No cached paint record for element.  (file:///Applications/Diffusion%20Studio.app/Contents/Resources/app/web/assets/index-CJwuYvmu.js:15)